A semiconductor wafer will be subjected to a number of manufacturing stages during fabrication of semiconductor devices included in the wafer. For example, numerous masking, patterning, etching, and film deposition processes may be performed over the frontside of the wafer in order to manufacture the multiple layers and features of a semiconductor device.
Alignment patterns are commonly used in semiconductor wafer processing to ensure accurate alignment of the various features of the multiple layers. Typically, the alignment patterns are configured so that they will be visible to alignment equipment at least from one side (e.g., the frontside) of the wafer. In addition, when a wafer is transparent to the illumination wavelength used by the particular alignment equipment that is used in the manufacturing process, the front side alignment patterns also may be visible through the wafer from the opposite side (e.g., the backside) of the wafer, thus allowing alignment of the opposite side. However, when a wafer is not transparent to the alignment equipment, or when the wafer backside is covered with an opaque material, alignment using frontside alignment patterns may not be possible. Accordingly, in such situations, frontside alignment patterns may not be useful in performing backside processing that requires alignment.